A Phoenix father is facing second degree murder charges for allegedly killing a man who allegedly harassed his young daughter.

Police say Melvin Harris, 40, admitted to beating Leon Armstrong, 26, to death after he attempted to break into the teenage girl's stall at a QuikTrip convenience store bathroom.

Harris was waiting for his daughter and her two friends in the store’s parking lot when Armstrong approached his car asking for money. Harris gave him change, then Armstrong walked into the convenience store, police said

Soon after, Harris' daughter and her friends came out of the store and said the man had harassed them, according to a police report.

Harris then went to the store and demanded that a security guard take action — or else he’d take matters into his own hands, police said.

Upon leaving the store, witnesses reported seeing Harris approach Armstrong, whom he then punched in the face, police said. Armstrong fell to the ground and Harris proceeded to stomp, kick and punch him until he was unconscious before driving off, police said.

After the assault, Armstrong was taken to a hospital with injuries including brain swelling and a a broken nose officials said.

Harris initially faced aggravated assault charges, but they were upped to second degree murder after Armstrong died.

“It is a horrible tragedy and QT will continue to assist law enforcement with their investigation," said Mike Thornbrugh, spokesman for QuikTrip.